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Engine basics => Engine set up tips => Topic started by: Mark Mc on July 22, 2017, 05:20:05 PM
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I bought a couple of used OS .25 LA-S engines last year from a couple of different guys for one of my projects. I finally got around to getting them ready to mount last night. Both are the blue bodied engines. Since I didn't want to use the remote needle valves, I had bought two of the stock OS needle assemblies to replace the nozzles in the venturi. The first one went in without any problems. The second one, though... When I pulled the nozzle out I found that the spraybar hole had been drilled out oversized. *SIGH* Pulling the venturi out and measuring it showed that it was a 7mm venturi. So much for using the spraybar I bought. So now what? I guessed I'd have to buy a new spraybar to fill out the hole in the engine body and take up the extra room in the venturi. Another delay on a project that's already been delayed quite a few months.
But, wait a minute! A couple of years ago I was at a swap meet and at one very messy table with all kinds of R/C and drone stuff a guy was selling a couple of Novel .061 CL engines N.I.B. for $20.00 each. I snapped them up. In another junk box was what looked like a locking CL spraybar and needle. I asked him what engine it was from. He had no idea what engine it was from, or even what it was because he had gotten it in a box of engine stuff he himself had bought at a swap meet sometime before. Since he had no idea what it was for, he said, "It's yours. Take it." So I did, and threw it in a box when I got home. Hmmm. Maybe it'll work. So I spent about an hour digging through boxes until I found it.
Eureka! It fits! Now to figure out if the .25 LA-S will run decently with it in the 7mm venturi. I don't need contest performance, as I'm still a beginner. But it'd be nice if it will give me a consistent run for three minutes. I didn't take any pictures of it before installation, but it looks like a brass assembly with two spacers on the barrel, a threaded end with two slits 180 degree apart cut through the threads, a cap to tighten down on the threads and lock the needle, and a needle with a bend on the end. Here's a picture of it mounted.
(https://s5.postimg.org/te2brxizb/DSCN5311.jpg) (https://postimg.org/image/nd4muuwcz/)
Anyone have any ideas on what assembly this is? Suggestions for starting turns open? Anything in particular I should know?
Thanks,
Mark
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Sorry, I didn't read if you put the measurement, but it looks like someone drilled the case for an ST style NVA. Is start with 3 turns out on suction. Leave the glo battery on while you turn it in a little to get it close. You'll hear it. I did my first stunt contest with that set up. 25 la on a ringmaster with an ST NVA. .250 venturi. It was very reliable. I too got mine used, already drilled out.
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Oh, just saw. The venturi is .275 on yours? That's a little big. I'd still run it. So run an 8 or 9 inch prop to keep the RPM up to get a great fuel draw.
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It looks like a KK Needle assembly
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Well, I finally got around to running this engine today, as I want to take it out to fly tomorrow. After replacing a bad glow plug, I played around with initial needle settings and got this thing to start up. After a little tweaking, I am very satisfied with this. Much finer control than the stock O.S. needle valve I was going to use. I was afraid that it would be too wide for the venturi, but it seems fine. I set it by my tach for 11K initially. Seems to run efficiently with the APC 10x4 prop I have on the engine. We'll see how it works tomorrow at the field.
Mark
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Mark, that's a long needle. To get it below the top of the fuselage and protect it, you could do what I did on my Shoestring. That's a wheel collar on the cut-down needle. I've been known to clobber one and bend it with my chicken stick too.
Rusty
(https://www.dropbox.com/s/2svsaubkq4wter3/Shortened%20NV.jpg?raw=1)